Bacterial infection is still a serious cause of hearing impairment. The purpose of this project is to understand the mechanism of bacterial infection by analyzing bacterial molecules that bind penicillin by cytochemical analyses. In order to localize molecules that bind with penicillin in bacteria, we developed a new technique. We conjugated penicillin with bovine serum albumin (BSA) and then with gold particles. Thin sections of Staphylococcus aureus were labeled with this probe. We found that penicillin-bindable molecules exist not only in the cell wall, but also in the surface coat and cytoplasm of Staphylococcus aureus. Some of the localization may represent novel molecules as well as known penicillin binding proteins. Lectins and their receptors are known to be involved in the bacterial adhesion to eukaryotic cells. Using agglutination assay and cytochemical techniques we found that wheat germ agglutinin-bindable substance in Staphylococcus saprophyticus and N-acetylglucosamine-bindable substance in red blood cells are involved in the adhesion of the bacterial to red blood cells.